The Internet small computer system interface (iSCSI) protocol is an Internet protocol (IP)-based storage networking standard for linking data storage facilities, developed by the Internet Engineering Task Force (IETF). By carrying SCSI commands over IP networks, iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances.
The iSCSI protocol is among the key technologies expected to help bring about rapid development of the storage area network (SAN) market, by increasing the capabilities and performance of storage data transmission. Because of the ubiquity of IP networks, iSCSI can be used to transmit data over local area networks (LANs), wide area networks (WANs), or the Internet and can enable location-independent data storage and retrieval.
Prior art FIG. 1 illustrates a network system 100 including both a host processor 102 and a transport offload engine 104 (i.e. TOE), in accordance with the prior art. As an option, such system 100 may be implemented in the context of the iSCSI protocol. Of course, however, such system 100 may be carried out in any desired protocol context.
In use, once communication across the network 116 is established using a connection or socket, the transport offload engine 104 receives packet data [i.e. iSCSI protocol data units (PDUs), etc.]. Once received, the transport offload engine 104 stores the data contained in the PDUs in a TOE buffer 112, in order to provide time to generate a data available message 117 and send the message to the host processor 102. The foregoing operation of the transport offload engine 104 may be governed by control logic 114 of the transport offload engine 104.
In response to a data available message 117, the host processor 102 generates a data list 106 [i.e. a scatter-gather list (SGL), memory descriptor list (MDL), etc.] that describes the location(s) in application memory 110 where the incoming data is ultimately to be stored. As shown, to accomplish this, the data list 106 may include at least one memory start address where the incoming data in each PDU is to be stored, with each start address followed by the length of a region in the application memory 110.
In use, the host processor 102 generates and associates the data list 106 with a socket (also known as a connection) associated with the received PDUs that prompted the corresponding data available message(s) 117. The incoming data contained in the PDUs is then copied from the TOE buffer 112 to the application memory 110 using the locations described by the data list 106 corresponding to that socket.
Thus, to receive a large number of PDUs via the network 116, the required size of the TOE buffer 112 may become excessively large. Unfortunately, a large TOE buffer 112 can not be implemented in a cost-effective manner on an integrated-circuit transport offload engine 104, since integrating on-board memory on the transport offload engine 104 is costly in terms of silicon die area, for example.
Therefore, there is a general desire to minimize, or even altogether eliminate, memory (i.e. see, for example, TOE buffer 112, etc.) on the transport offload engine 104 for providing a cost effective transport offload engine 104.
There is thus a need for a cost effective technique of managing received PDUs using data lists (i.e. SGLs, MDLs, etc.) in the context of a transport offload engine.